We built the climbing stand (pictures will follow), out of a 2’x2′ heavy & thick piece of wood for the base, added a 5′ tall 4×4 cedar post glued and screwed in. Then we added four platforms, each 1’x2′, at 13″ intervals from the ground, leaving an 8″ jump at the top to the window sill.
Each platform was notched and attached around the 4×4 post and screwed in with a brace underneath.
Each platform also had carpet stapled to it.
So far only one uses it regularly but the others are looking at it.